Denial is not absence — detection learns the unverifiable answer 06 ruled for it

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

KanbanTests/GitUndoTests.swift

@@ -1123,6 +1123,30 @@ struct GitUndoBindingTests {
         #expect(session.git?.committer == nil, "no committer, and so nothing that could write there")
     }
 
+    @Test("The default provider closure binds the native stack on an unverifiable board too")
+    func proOnAnUnverifiableBoardBindsTheNativeStack() throws {
+        // "`unverifiable` joins the same branch structurally" (`AppModel.makeHistoryProvider`) — a
+        // denied ancestor check is no more a repository the app manages than a repo-nested one is.
+        //
+        // This exercises the seam directly rather than through `openBoard`: reaching `.unverifiable`
+        // on a real board needs a denied *ancestor*, and POSIX permission bits (unlike the sandbox's
+        // independent per-path grants) cascade — chmoding a real ancestor to deny its `.git` check
+        // also denies reading the board's own files underneath it, so the board could never actually
+        // open (`BoardGitModeDenialTests` in `BoardGitModeTests.swift` covers the detection axis
+        // itself against real denied directories; this covers what the composition root does with
+        // whatever mode a `HistoryStore` reports, real detection or not).
+        let fixture = try makeBoard()
+        defer { fixture.tearDown() }
+        let store = try BoardStore(rootURL: fixture.root)
+        let (model, tearDown) = try makeModel()
+        defer { tearDown() }
+
+        let git = HistoryStore(boardRoot: fixture.root, mode: .unverifiable, ledger: EchoLedger())
+        let provider = model.makeHistoryProvider(store, .pro, git)
+
+        #expect(provider is NativeHistoryProvider)
+    }
+
     @Test("The free tier's repo-nested board still binds the native stack — it never detects one")
     func freeTierOnARepoNestedBoardIsNativeToo() throws {
         let outer = try WriterFixture()